During repression of alkaline phosphatase by sodium lactate in Bacillus licheniformis 749/C cells neither the total protein synthesis nor the membrane bound penicillinase synthesis is affected. It appears that lactate repression is caused by a specific effect on alkaline phosphatase synthesis and does not arise from nonspecific effect on general protein synthesis. Interrelationship of the gluconeogenesis and alkaline phosphatase repression is suggested from the preferential incorporation of lactate molecule into glycogen during repression by lactate. Alkaline phosphatase proteins from 0.1% glucose derepressed and 2% lactate repressed cells are purified from IM magnesium acetate extract by DEAE sephadex and sephades G-200 gel filtration chromatography. Electrophoresis of both the proteins in SDS and nondenaturing polyacrylamide gel gives rise to distinct single bands. Ultracentrifugal analysis confirms the purity of the proteins. Both the proteins having 105,000 molecular weight are composed of 60,000 molecular weight subunits. Amino acid analysis of enzymes from lactate and glucose grown cell (L- and G-enzyme respectively) differ only in arginine content. Both the enzymes contain zinc. After removal of the metal ions, L-enzyme in contrast to G-enzyme is irreversibly inactivated. The L-enzyme is more sensitive to inorganic phosphate inhibition and has lower Km that G-enzyme. The L-enzyme could cleave ATP and inorganic phyrrophosphate, (this activity is not present in G-enzyme) and has greater transphosphorylase activity than G-enzyme. Finally, L-enzyme though cross reacts with antibody against G-enzyme, appears to be less sensitive in binding to the antibody. The results suggest that gluconeogensis controls the alkaline phosphatase molecule by altering its conformation and functional characteristics.